Qarn, tank does have to try and stun, and CD through it, but DPS should never be so low as to see final sting, ever.
Ive never seen final sting when im DPSing with someone else who is roughly on par or better than me.

w/o tank stance, final sting will do all of your HP in dmg if no CD i sup.
(I think you have like 2-2.2k hp, and it does 2-2.5k hp in dmg. with a tank stance or a single CD, and at full HP, you'll survive. there is a pull with double final stings, to which you need 1 killed, and stun the other, or CD through it.)
But jsut wait till Lv63+ dungeons, when tanks are so under geared they go from full HP to 20% hp in a single GCD. And wait till one round and they get crit by a few enemies, they are as good as dead if they have no CD up. (and if its proc based, like anticipation/bulwark, and fails to lower dmg, AND the crits go out, as they cant be parried/blocked.)